What is delegate pattern in iOS?
What is delegate pattern in iOS?
Delegation is a simple and powerful pattern in which one object in a program acts on behalf of, or in coordination with, another object. The delegating object keeps a reference to the other object—the delegate—and at the appropriate time sends a message to it.
How do delegates work iOS?
A delegate allows one object to send messages to another object when an event happens. The delegating object keeps a reference to the other object–the delegate–and at the appropriate time sends a message to it.
How do you implement delegates in Swift?
The basic steps to use delegation are the same for both Objective-C and Swift:
- Create a delegate protocol that defines the messages sent to the delegate.
- Create a delegate property in the delegating class to keep track of the delegate.
- Adopt and implement the delegate protocol in the delegate class.
What’s the difference between KVO and delegate?
KVO is useful to listen “without the class knowing”, although of course that’s not the case, the class on which KVO is applied does not need to be changed. Delegation is a design pattern that you use when you want some other object to modify the sender’s behavior.
What is difference between delegate and datasource in iOS?
A data source is almost identical to a delegate. The difference is in the relationship with the delegating object. Instead of being delegated control of the user interface, a data source is delegated control of data.
Why do we use delegates in Swift?
Delegation is used for everything from handling table view events using UITableViewDelegate , to modifying cache behavior using NSCacheDelegate . The core purpose of the delegate pattern is to allow an object to communicate back to its owner in a decoupled way.
What is the difference between delegate and protocol in Swift?
We can say Protocol as a set of rules. That rules can be optional or required like we have to use in protocol. Delegates is a message passing technique in objective C and swift. An object has to take care of that message.
What is KVC and KVO?
KVC stands for Key-Value Coding. It’s a mechanism by which an object’s properties can be accessed using string’s at runtime rather than having to statically know the property names at development time. KVO stands for Key-Value Observing and allows a controller or class to observe changes to a property value.
Why is delegate weak in IOS?
The reason that objects weakly retain their delegates is to avoid retain cycles. Imagine the following scenario: object a creates b and retains it, then sets itself as b ‘s delegate. a is released by its owner, leaving a retain cycle containing a and b . This is actually a very common scenario.
Should all delegates be weak?
Most delegate protocols are situations where the object in question has no business claiming ownership over the delegate, but merely where the object in question is providing the ability to inform the delegate of something (or request something of it). Delegates should always generally be weak.
How are delegate patterns used in iOS development?
This enables the delegate to customize the base class. Delegation is frequently used in practical iOS development. The iOS delegate pattern has a significant impact on the platforms of Apple. A delegation pattern allows one delegating object to send messages to another object when a specific event happens.
How is the delegate protocol used in Swift?
Delegates are a design pattern that allows one object to send messages to another object when a specific event happens. The delegation design pattern in swift is used for many things such as from handling table view events using UITableViewDelegate, to modifying the cache behaviour using NSCacheDelegate.
How are protocols used in delegation design pattern?
In the delegation design pattern, protocols serve the same kind middle-man role as a contract. To the delegator class, the protocol is a guarantee that some behavior will be supplied by the other party (the delegate).
What does delegation mean in the Apple documentation?
The official Apple documentation defines delegation as: Delegation is a design pattern that enables a class to hand off (or “delegate”) some of its responsibilities to an instance of another class. That’s quite complex, so let’s break it down… Think about delegation in the real world.